This invention relates to a machine for inserting pins into circuit boards.
Many computers and other electronic devices use a back panel, or motherboard, in a cabinet with a series of connectors into which individual circuit boards are inserted. The connectors are composed of parallel rows of metal pins which provide both a structural connection and an electrical connection between the motherboard and the circuit boards. The connectors are formed by inserting the pins into holes in the motherboard. The holes in the motherboard are typically plated with a metal to form an electrical connection, or the ends of the pins may be wire-wrapped to form electrical connections.
The individual pins typically have a widened shoulder portion near the middle which stops the pin from being pushed completely through the motherboard and also provides a surface for pushing against the pin to insert it into the motherboard. The pins are typically made by punching them out of a metal strip giving a comb-like structure with the pins connected at one end by a carrier strip to form a webbing. This webbing may either be continuous or may form a short `comb` with a fixed number of pins.
A comb webbing can be grasped with a special pair of jaws and hand-inserted into the motherboard. Shultz, Jr. et al., U.S. Pat. No. 3,875,636, shows such a pair of jaws. Care must be taken to insert the pins without bending them or damaging the sides of the holes in the motherboard which are coated with a metallic layer to provide an electrical connection. After the pins have been inserted, the webbing can be bent to break the pins free and the pins can then be aligned by tapping the pins with a ruler-like device between adjacent rows of pins or by similar means. These steps must be done carefully to avoid excessive damage to the holes in the motherboard.
Automatic pin inserting machines which insert one pin at a time into the motherboard also exist. There are, however, obvious limitations in the speed of such a machine. Machines which insert more than one pin at a time use a pair of jaws to grasp the comb of pins. Such a pair of jaws would have slots on its interior surface to accommodate the pins, such as shown by Cobaugh et al. in U.S. Pat. No. 3,946,477.
In order to prevent misalignment of the pins and avoid damage to the holes and circuits of the motherboard, it is desirable to separate the pins from the carrier strip before insertion. This can be done by grasping the webbed pins with a pair of jaws and then removing the carrier strip with a punch, such as shown by Chisholm in U.S. Pat. No. 4,216,580. The Chisholm device shows a comb of pins being inserted into the jaws and a punch attached to one jaw severs the pins from the carrier strip as the jaws are closed. The jaws could then be used to insert the pins in the motherboard. Chisholm also shows the comb of pins being connected at their bottom end as well as their top end and the carrier strip on the bottom end being removed by enclosing the carrier strip in a channel which is rocked back and forth to bend the carrier strip and break the carrier strip from the pins. In order to thereafter insert the pins in the motherboard, the channel would have to be removed from beneath the jaws.
In order to increase the speed of a pin inserting machine, one can use a continuous webbing which is wound on two reels like a movie film. Such a method of using a continuous webbing is shown in Chisholm, U.S. Pat. No. 4,265,508. The continuous webbing of pins is fed through a first position where the pins are grasped by a clamping mechanism and the carrier strip is severed from the pins by a punch and die operation. The clamping mechanism, which is located on a turret, is then rotated 90 degrees to place the pins directly above the motherboard. The clamping mechanism is then lowered to insert the pins into the motherboard. The use of the turret allows the clamping mechanism to be rotated away from the carrier strip so that the clamping mechanism can be lowered to insert the pins without interference from the carrier strip. Unfortunately, the turret adds complexity and more moving parts, which have to be aligned, to the machine.